SlimBatteryMonitor is a replacement power gauge for Apple's Mac OS X that tracks both laptop batteries and many UPS batteries. Multiple-battery systems (e.g. older powerbooks) are supported as well. A graphical icon shows the power remaining, and can be accompanied by a text description (battery charge in percent, or time remaining). Colours can indicate whether the system is fully charged, charging or on battery.

From the web site:
"Does SlimBatteryMonitor support Intel macs? When will a universal binary be available?

The current version of SlimBatteryMonitor has been reported by several users to run fine on Intel Macs. (It runs seamlessly in Apple's Rosetta emulator.)

A new version of SlimBatteryMonitor with a few small new features is currently in development. When that version is released it will be in the new Universal Binary format that will run natively on both PowerPC and Intel-based mac computers."